On Wednesday morning in the wake of the attacks in Brussels, Mr Turnbull "strongly encouraged" union members to rethink the industrial action and urged them "to pursue their complaints, their disagreements with the government through other means".

CPSU national secretary Nadine Flood said the union had agreed to postpone the strike and was "conscious of the understandable concern of travellers in the wake of the Brussels attack".

Advertisement

"We will consider whether to undertake further industrial next week and in coming weeks in light of the department and government's response in coming days," she said.

The airport attack occurred at the check-in area where no one needed to present a boarding pass or identification to be present.

Customs and Immigration staff have already launched stop work action at airports in Darwin, Adelaide, Cairns, Townsville and Perth to protest a breakdown in negotiations over pay and entitlements.

Larger disruptions and lengthy delays were likely on Thursday when staff at Melbourne, Sydney and Brisbane airports were expected to walk off the job for 24 hours.

Department of Agriculture staff working in biosecurity were also expected to walk off the job at major airports with rolling industrial action to continue in coming weeks.

Ms Flood acknowledged the strike action may have added to the apprehension of some travellers boarding international flights over the Easter weekend.

On Wednesday morning, public service commissioner John Lloyd said he was hopeful the union would heed the Prime Minister's call.

"It is time for them to demonstrate responsibility and an awareness of national concerns beyond their immediate industrial strategy," he said.

Mr Lloyd has condemned proposed strike action at international airports as cynical and deliberately designed to cause maximum disruption.

Mr Turnbull said security at international airports would not have been undermined by the strike action as it was primarily the concern of the Australian Federal Police, rather than the Australian Border Force.

The Australian Federal Police has increased security operations and patrols at the country's major international airports in the wake of the deadly attack

"Security measures at these airports are multi-layered and may involve armed mobile, canine and foot patrols, static guarding as well as specialist response armed capability," an AFP spokeswoman said.

"A range of technical measures such as extensive CCTV also support these security measures."

The Department of Foreign Affairs and Trade has advised Australians to reconsider travelling to Belgium